1. Field of the Invention
The present invention relates to a method for compressing dynamic image information which is capable of processing compression of quantity of dynamic image data at high speed with high compression rate, and a system therefor.
2. Description of the Prior Art
In recent years, many such algorithmic methods for stationary and dynamic image compression as disclosed in U.S. Pat. No. 5,164,819 have been standardized because of their high efficiencies which utilize discrete cosine transformation (hereinafter referred to simply as DCT) using only cosine function in orthogonal transformation encoding in a dynamic image frequency band and having excellent power concentration to low-frequency components. In these, an image is divided into small blocks of N pixels in each of horizontal and vertical directions (small blocks each composed of N.times.N pixels), each of the small blocks of the image is subjected to two-dimensional DCT and then encoded by allocating an appropriate number of bits thereto. After the establishment of JPEG (Joint Photographic Experts Group which was formed by ISO and CCITT jointly. The standard proposed by the JPEG is also called JPEG), an algorithmic method was proposed as a standard which is based on adaptive discrete cosine transformation (ADCT mode) capable of providing most preferred encoded image quality.
The proposed method is systematized such that an image of 8.times.8-pixel blocks is subjected to two-dimensional DCT in terms of each block of 8.times.8 pixels as a unit to obtain DCT coefficients, each of the coefficients is linearly quantized by using quantized matrices with different quantized step sizes assigned to the respective coefficients, and that with respect to direct current components, each difference between a direct current component and that of the neighboring block on the left is quantized, and that with respect to alternating current components, they are first zigzag-scanned and rearranged in one-dimensional array, and each coefficient is examined whether it is zero or not, and consecutive zero coefficients has its length counted as a run length, and on detection of a non-zero coefficient, result of quantization thereof is subjected to two-dimensional Huffman coding in combination with a run length of the preceding zero coefficients (as for Huffman coding, see D. A. Huffman, "A Method for the Construction of Minimum Redundancy Codes", Proc. IRE, 40, 10, pp. 1098-1101 (September 1952)).